Common Key Sharing Method and Wireless Communication Terminal in Ad Hoc Network

1. A common key sharing method in an ad hoc network constituted by wireless communication terminals implemented with relay functions thereon, comprising: a common key generating step in which a first wireless communication terminal responsible for relaying generates a common key shared within said ad hoc network; a common key distributing step in which said first wireless communication terminal responsible for relaying distributes said common key to each of a plurality of other wireless communication terminals within a wireless communication area; and a transferring step in which each of said plurality of wireless communication terminals which received said common key holds said common key, and when one or more of said plurality of wireless communication terminals are responsible for relaying, said plurality of wireless communication terminals being responsible for relaying transfers said common key to other one of each of said plurality of wireless communication terminals within a wireless communication area.

2. The common key sharing method according to claim 1 , comprising, an inter-transmission-area distributing step in which the first wireless communication terminal distributes an inter-transmission-area key to each of the plurality of wireless communication terminals within the wireless communication area, wherein, said inter-transmission-area distributing step encrypts said common key with said inter-transmission-area key, and distributes said common key thus encrypted.

3. The common key sharing method, according to claim 2 , comprising, a mutual authentication step which performs mutual authentication between the first wireless communication terminal and each of the plurality of other wireless communication terminals within the wireless communication area, wherein, said inter-transmission-area distributing step distributes said inter-transmission-area key to the second wireless communication terminal thus authenticated.

4. The common key sharing method according to any one of claims 1 to 3 , wherein, said common key is identifiable according to an identifier.

5. The common key sharing method, according to claim 4 , wherein, said identifier is generated, distributed, and transferred, together with said common key.

6. The common key sharing method according to claim 1 , wherein said common key is an ad-hoc-network common key shared in common by at least three of the wireless communication terminals of the ad hoc network.

7. A wireless communication terminal implemented with a relay function for constituting an ad hoc network, comprising: a network information generating means in which said wireless communication terminal sends/receives information regarding network configuration to/from each of a plurality of wireless communication terminals within a wireless communication area and generates network configuration information; a common key generating means in which said wireless communication terminal generates a common key to be shared within said ad hoc network when said wireless communication terminal itself being determined as responsible for relaying based on said network configuration information; a common key distributing means in which said wireless communication terminal distributes said common key thus generated to each of the plurality of wireless communication terminals within the wireless communication area; and a transferring means in which when each of the plurality of wireless communication terminals receives said common key, each of the plurality of wireless communication terminals holds said common key, and transfers said common key thus received to other one of each of the plurality of wireless communication terminals within the wireless communication area, when each of the plurality of wireless communication terminals itself being determined as responsible for relaying.

8. The wireless communication terminal according to claim 7 , comprising an authentication means, which authenticates each of the plurality of wireless communication terminals within the wireless communication area, wherein, said network information generating means sends/receives the information regarding the network configuration to/from each of the plurality of wireless communication terminals, which has been authenticated.

9. The wireless communication terminal according to claim 8 , wherein, said network configuration information is an information to recognize the wireless communication terminals constituting the ad hoc network, and when each of the plurality of wireless communication terminals having been authenticated moves out of the wireless communication area and each of the plurality of wireless communication terminals is not recognized as the wireless communication terminal constituting the ad hoc network within a predetermined period of time, said common key generating means updates the common key, and said common key distributing means distributes said common key thus updated.

10. The wireless communication terminal according to claim 8 , wherein, said network configuration information is an information to recognize the wireless communication terminal constituting the ad hoc network, and when each of the plurality of wireless communication terminals having constituted the ad hoc network moves out of the ad hoc network and returns into the wireless communication area within a predetermined period of time, said authentication means does not authenticate each of the plurality of wireless communication terminals.

11. The wireless communication terminal according to claim 7 , wherein said common key is an ad-hoc-network common key shared in common by at least three of the wireless communication terminals of the ad hoc network.